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Description  |
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TECHNICAL FIELD
This invention is related to broadcast video and more particularly to the
insertion of advertising in video distribution systems.
BACKGROUND ART
Broadcast video sources (i.e. TV networks, special interest channels, etc.)
schedule their air time with two types of information: "programming" for
the purpose of informing or entertaining, and "avails" for the purpose of
advertising. The avails may occupy roughly 20-25% of the total
transmitting time, and are usually divided into smaller intervals of 15,
30, or 60 seconds. While the video sources usually know what programming
is to be sent during a specific interval (i.e. Seinfeld, Thursdays at 9:00
pm), and usually also know the number and timing of avails, there are some
types of events (i.e. sporting, live broadcasts) where these are not
precisely known.
Information about avails is provided to the sales department of local
stations which sell the commercial time. The sales department may have
many individuals trying to sell the same avail to different prospective
clients, once at the national level, and multiple times for each local
distribution system (i.e. cable head-end or local broadcast station.) If
an avail has not been sold locally, the national spot is shown.
Once sold, the content must be produced and provided to the operator of the
distribution system. The content must be made available to the local
distribution feed during each time it is scheduled.
The timing of the cutover for a single commercial is illustrated in FIG. 1.
Approximately 5 seconds before the beginning of the commercial break, a
pre-roll cue is issued over a signaling channel. At this time, a video
playback device begins to synchronize its output with that of the network;
a latency of several seconds is normal for analog playback decks. A start
cue arrives at the beginning of the commercial, indicating that the
network has faded to black and a switch should select the local source.
Note that the network feed may continue to supply national advertising
which is not sent to the local distribution system. At the conclusion of
the ad, a return cue switches the video source back to the network, and
the local playback deck stops briefly afterward.
Commercials and breaks are not always exact multiples of 30 seconds. It is
therefore possible for the local ad to end slightly before or after the
network break. It is up to the local system to establish a policy whether
to return immediately upon receipt of the cue, or whether to allow the
local commercial to air in its entirety.
Commercial breaks typically allow more than one local ad. Depending on the
number of ads sold for a given time slot, the system may return to the
network feed early--after the local spots have been played--or it may
continue to run local commercials for the duration of the break. The video
playback device not only must often serve more than one ad, but often may
also be shared among multiple channels. The server must therefore have
enough capacity to hold all local ads currently airing, and must be able
to access a predefined set of ads for an upcoming commercial break within
a few seconds of the first cue.
A typical analog ad insertion system of the prior art is illustrated in
FIG. 2. The broadcast source, 200, for example, is an RF channel analog
network feed received from a satellite, which includes cue tones modulated
on a side carrier. The receiver/demultiplexer 210 demodulates the analog
video from the RF carrier, and demodulates the signaling tones from the
side carrier and generates control information such as contact closures
which are passed to an analog matrix switch 220. The matrix switch is an
intelligent device which controls an external tape library/robot system
and which knows which commercials are to be played during a given break.
Commercial systems utilize the same switch and tape library to support
multiple channels.
As discussed above, the preroll cue 240 tone is detected in the matrix
switch prepared for the start of the advertisement. When the start cue is
detected (250), the analog output 230 is switched from the network feed
originating through receiver/demultiplexer 210 to the local analog matrix
switch where the advertisement is provided. Line 260 between the
receiver/demultiplexer and the local analog matrix switch indicates that
the two devices are synchronized so that when switch 270 is activated to
switch the programming source, the transition can be made without a loss
of synchronization at the receiver.
For use with a digital video dial tone network, the output of the analog
system 230 must be encoded by a real-time encoder (not shown). There is a
slight possibility that a commercial would suffer from unpredicted
distortions during some playbacks through the real-time encoder. Of
greater concern is the constant wear on tapes and tape players which
require constant human maintenance to avoid degraded quality.
FIG. 3 illustrates an end-to-end view of a video distribution system over
an analog network of the prior art. Video programming is provided by a
digital video-on-demand server 300, the output of which, because the
network is analog, is converted to analog in digital-to-analog converter
(DAC) 310. The digital output of the digital VOD server can be, for
example, in MPEG-2 format over ATM. The output of DAC 310 is fed to analog
network 330 which also receives an analog feed 320 from, for example,
satellite receiving equipment. The output of analog network 330 is fed to
circuitry, such as shown in FIG. 2, where local analog advertising is
selectively inserted in response to cue tones. The output of the FIG. 2
circuitry is fed to analog digital converter, (ADC) 350 which converts
back to the digital format for display on a digital display device 360.
Since modern production studios are utilized in the production of
advertisements, the ads are created in digital form. The multiple
conversions from digital to analog and back to digital are undesirable.
Such conversions can affect reliability and image quality. One cannot
merely relocate block 340 to the left of the DAC 310 because MPEG and ATM
streams cannot be switched at arbitrary points.
FIG. 4 illustrates a variation on the previous approach. Analog cable
operators have recognized the tape maintenance drawbacks, so some vendors
have begun substituting digital video servers 400 with analog outputs for
the tape libraries in FIG. 2. While the commercials reside on the disks in
digital form, a decoder 410 is employed which provides a conventional
analog output.
Digital servers respond more quickly to cue signals, allowing greater
flexibility for unanticipated avails. However, because the analog switch
output must be fed to the digital network input, commercials will received
two concatenated lossy encoding/decoding operations.
The transmission of programming, in particular, video programming where
wide bandwidth is required, has been known to include a variety of
compression techniques. Modern decoders of compressed video information
will adapt their operating modes in dependence upon the properties of the
incoming signal. Video programming is often distributed in multiplexed
format which requires that either the decoder or an associated
demultiplexer be aware of where in the multiplexed stream particular
programs are located.
One of the widely accepted standards for the distribution of video
programming is that promulgated by the Organisation Internationale de
Normalisation (International Organization for Standardization) under
Standard ISO/IEC JTC1/SC29/WG11 entitled "Coding of Moving Pictures and
Associated Audio". The particular working group responsible for that
standardization effort is also known as the Motion Picture Experts Group.
MPEG compression and decompression standards have been evolving. The
current advanced version is generally known as MPEG-2. The MPEG-2 standard
is hereby incorporated by reference in its entirety. In the language of
the MPEG-2 standard, a "program" is comprised of typically a source of
video and a source of audio which share a common time base. One or more
elementary digital streams (e.g. video or audio), as well as other data,
are combined into single or multiple streams which are suitable for
storage or transmission. System coding follows the syntactical and
semantic rules imposed by the MPEG-2 specification and provides
information to enable synchronized decoding without either overflow or
underflow of decoder buffers over a wide range of retrieval or receipt
conditions.
Under the MPEG-2 standard, an incoming individual video signal and related
audio signal are encoded and packetized into a respective Video Packetized
Elementary Stream (PES) and Audio Packetized Elementary Stream. The video
and audio PES from one or more programs are combined into a transport
stream for transmission or storage.
The transport stream is designed for use in environments where errors are
likely, such as storage or transmission in lossy or noisy media. Transport
stream packets are 188 bytes in length. Transport stream packets are
generally divided into two sections. The first section constitutes header
information and the second constitutes payload. Header information
includes, inter alia, a synchronization byte, transport scrambling control
and a thirteen bit program identification (PID) indication. PID value 0 is
reserved as an indication that the packet includes program association
table data. PID value 1 is reserved for conditional access such as
encryption. PID value 0.times.1FFF is reserved for administrative (no-op)
packets utilized for synchronizing the link. Other program identification
numbers are utilized to identify transport packets with the program source
from which they originate.
FIG. 5 depicts a transport stream utilizing the MPEG-2 standard. As
indicated above, each transport packet in the transport stream carries a
program identification number (PID). PID 0 carries program association
table information. As illustrated in FIG. 5, a program association table
maps a particular program source with the location of the PID associated
with a program map related to that source. Thus, the program association
table defines the location of program maps for each source of programming
in the transport stream. The program map for CBS is found in PID 132; the
program map for NBC is found in PID 87 and so forth.
The program map for CBS illustrated in FIG. 5 as that associated with PID
132 identifies the PID numbers for the packetized elementary streams (PES)
for the video and audio channels associated with the program. One should
note at this time that more than two PID's may be associated with a
program. For example, there could be a data channel associated with the
program which would include data for closed captioning for the hearing
impaired. There could be a number of audio elementary streams for, for
example, respective different languages. Thus the programming map provides
some flexibility beyond that required for merely associating a single
video and audio elementary streams.
Once the program map is known, the program decoder can be set to extract
the desired elementary streams (e.g PID 56 in FIG. 5 and PID 74 shown in
FIG. 5) for decoding and presentation. Transport packets of PID=56
represents the video elementary stream associated with CBS' MPEG video
system. Within CBS' video elementary stream are video sequence headers
which define things like frame rate, resolution, and the coordinates on
the screen where display of the image should begin. Such coordinates are
useful, for example, in defining pictures within a picture when multiple
pictures are superimposed. After the video header sequence, the normal
video syntax occurs which, in the case of MPEG, includes the normal frames
associated with video compression such as I frames and B frames used in
MPEG.
The elementary stream with PID=74 is the audio stream associated with the
video shown in transport packets with PID=56 as defined in program map at
PID=132.
A typical MPEG-2 transport demultiplexer and decoder is shown in FIG. 6.
The data link specific interface 610 converts the incoming data link
format (e.g. optical fiber encoded data) to a form (e.g. electrical) for
demultiplexing and decoding. Transport stream demultiplexer 620 monitors
the PID's of the incoming transport stream packets to identify those
selected for decoding and routes those to respective video (630) and audio
(640) decoders. Since the video and audio associated with the same program
are derived from a common clock, clock control 650 drives both decoders.
Note that the transport stream demultiplexer includes functionality, such
as that described in connection with the description of the transport
stream of FIG. 1, necessary to identify the particular PID's needed to
extract information from the transport stream to present the desired
program to the user.
The Motion Picture Experts Group (MPEG) is believed to be working on
additional standards which may be implemented in the fully digital network
environment. As of now, however, there are no products available to
implement ad insertion in fully digital environment.
There are a number of problems with the prior art, Analog recorders are
subject to serious wear and tear which results in reduced reliability. In
addition, analog recorders do not match the digital end devices and the
digital production facilities used to create advertisements for insertion
in programming to be delivered to an end user. In addition, the spin up
latency of analog recorders is slow. Excessive digital-to-analog followed
by analog-to-digital conversion results in a degradation of image quality
from the original.
Even in a fully digital system as currently implementable, when attempting
to switch programming from one source to another, the switching tends to
introduce interference, to cause loss of synchronization, to cause
excessive retransmissions, or to freeze the decoder by switching in the
middle of a packet or in the middle of a frame. These result in error
conditions in the decoder and/or in unpredictable screen displays.
Further, in the prior art, there is generally one device per network feed.
Some network feed ad insertion techniques of the prior art do not provide
a smooth transition from the network feed to the advertisements and back.
Accordingly, one advantage of the invention is avoiding the problems of the
prior art by providing digital ad insertion techniques which permit a
switch from one program source to another smoothly without excessive
analog to digital conversion and back and without the wear and tear of
analog recorders and their accompanying slow spin up latency.
Another advantage of the invention is provision of digital ad insertion in
which switching occurs predictably at the end of packets and frames so
that undesired error states are not encountered.
Another advantage of the invention is in the use of one set of hardware to
service multiple lines and to provide correct and smooth transition from
network feeds to advertisement sources without the difficulties of the
prior art.
Another advantage of the invention lies in the implementation in a smart
communications interface board with simple software enhancements.
DISCLOSURE OF THE INVENTION
These and other objects of the invention are achieved by providing methods
and apparatus for inserting local video programming in place of externally
supplied programming. Externally supplied programming contains embedded
tone cues including a pre-roll cue and a roll cue, which are detected
prior to converting the analog video information to digital video
information. A digital video player is activated in response to one of
said tone cues preparatory to initiating playback. Playback is initiated
from said recorder in response to detecting an idle condition from said
digital video information. Idle condition is detected by detecting idle
MPEG packets or by detecting a series of black pixels. An output buffer
may be pre-filled in response to one of said tone cues and read out in
response to said detecting an idle condition. In a time division multiplex
system, at least one time slot is monitored to determine when an idle
condition exists. In a MPEG or ATM system, packet headers are monitored
for particular source or destination addresses. Playback begins at a point
in the video frame which is the same as the point at which the information
from the externally supplied programming left off. Typically, this will be
a frame boundary or a packet boundary.
The invention is also directed to apparatus for inserting local video
programming in place of externally supplied programming which receives
externally supplied programming from a plurality of sources. Each source
provides programming including analog video information and embedded tone
cues. The analog video information is converted to digital video
information. A memory stores a plurality of local programs. Each of said
sources is monitored to detect one or more tone cues. In response to one
tone cue from a source, the memory is prepared for playback of one or more
local programs which are to be substituted for said externally supplied
programming from that source. Playback from said memory of respective one
or more of said local programs to be substituted for said externally
supplied programming is initiated by detecting an idle condition from said
digital video information from said source. A plurality of buffers smooth
the transition to the local programs replacing externally supplied
programming from individual sources.
A plurality of cue tone protocols are serviced which can be unique to each
of the plurality of sources (i.e. different networks use different tone
protocols).
The invention is also directed to a method for inserting local video
programming in place of externally supplied programming by receiving
externally supplied programming comprising analog video information and
embedded tone cues (including a pre-roll cue and a roll cue), detecting
said tone cues and converting the analog video information to digital
video information; activating a video recorder in response to one of said
tone cues preparatory to initiating playback; and initiating playback from
said recorder in response to detecting an idle condition from said digital
video information. An estimated time from roll cue detection to end of a
current frame or current packet is calculated and a buffer pre-filled with
an amount of data from said recorder. Data from said buffer is read out at
said estimated time.
The invention is also directed to a method for inserting externally
supplied programming in place of local video programming by receiving
local digital video programming and providing it to a user, receiving
externally supplied analog video programming and embedded tone cues
including a return to network cue, detecting said return to network cue,
converting said analog video information to digital video information upon
receipt of said return to network cue and terminating operation of a video
recorder in response to said return to network cue.
The invention is also directed to a method for inserting local video
programming in place of externally supplied programming by receiving
externally supplied programming from a plurality of sources, each source
providing programming comprising analog video information and embedded
tone cues, and for converting the analog video information to digital
video information; providing a memory for storing a plurality of local
programs; monitoring each of said sources to detect one or more tone cues
for preparing said memory for playback of respective one or more of said
local programs to be substituted for said externally supplied programming;
and initiating playback from said memory of respective one or more of said
local programs to be substituted for said externally supplied programming
from a source when a respective source is determined to be idle.
The invention is also directed to a method of facilitating smooth
transitions from a source of analog video information to a digital source
of local information, by converting analog video information to digital
and attaching one or more all-black frames at the beginning of said analog
video information.
The invention is also directed to a method of facilitating smooth
transitions from digital source of local information to a source of analog
video information by attaching one or more all-black frames at the end of
said local information.
Still other objects and advantages of the present invention will become
readily apparent to those skilled in the art from the following detailed
description, wherein only the preferred embodiment of the invention is
shown and described, simply by way of illustrations of the best mode
contemplated of carrying out the invention. As will be realized, the
invention is capable of other and different embodiments, and that several
details are capable of modifications in various obvious respects, all
without departing from the invention. Accordingly, the drawings and
description are to be regarded as illustrative in nature, and not as
restrictive.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a timing diagram showing how ad insertion is cued by the network.
FIG. 2 is an illustration showing prior art analog ad insertion techniques.
FIG. 3 is an illustration of end-to-end program distribution with ad
insertion operating over an analog network as done in the prior art.
FIG. 4 is an illustration showing a prior art work around design to allow
digital storage to be utilized.
FIG. 5 is an illustration of an MPEG 2 transport stream of the prior art.
FIG. 6 is an illustration of an MPEG 2 decoder at a high level.
FIG. 7 illustrates a digital ad insertion technique according to the
invention.
FIG. 8 is an illustration of a multi-channel digital ad insertion technique
in accordance with the invention.
FIG. 9 is an illustration of some of the details of the FIG. 8 embodiment
of the invention.
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 7 illustrates a single channel embodiment of methods and apparatus for
digital ad insertion in video programming.
Analog video source 700 receives programming from, for example, a network
feed or a video on demand server. That analog video source is converted to
digital in analog-to-MPEG-2 converter 710 and the output is buffered at
720 for transmission to users in digital over output port 780. Cue
detector 730 detects cue tones from the video provider, which in most
cases are network specific. State control 740 responds to cue detector 730
to trigger appropriate logical processing for MPEG-2 analog-to-digital
converter 710 and digital video recorder 750, each with respective output
buffering 720 and 760.
When the start-cue is received from the network and detected in cue
detector 730, the video encoder 710 is signaled to complete its current
frame. Note that since digital video output lags input by about 0.5-1.0
seconds, the last digitized frame should be the network's fade to black.
When the server 755 is signalled by idle detection 770 that there is a
lack of input, it begins to send advertising output to digital video
output port 780.
Idle detection can be accomplished by either looking for an absence of
packets addressed to a particular destination or by idle packets such as
idle MPEG or ATM or TDM packets.
Shortly before the network break is over, the encoder 710 is signaled to
restart. This request may be anticipated by the server which can tell
approximately by the end of advertising content that a network feed will
again be required. The encoder has start-up latency as it sends out its
first encoded frame, but the server can always select its timing such that
an underflow condition occurs. This eliminates the possible corruption of
the MPEG stream which could result in decoder artifacts and instead shows
a brief black screen before the channel feed from the network resumes.
Thus, a black frame is preferably appended to each commercial produced for
use on the system. Thus, by sending a substantially black frame as the
last frame of digital information, an MPEG encoder will freeze the last
frame of information until such time as good information is provided from
a different source. Thus, when a black frame is sent as the last frame of
the advertising, underflow occurs, the MPEG decoder freezes at a black
frame and is thus ready to receive new information from the network feed.
Block 795 groups several functions together which are preferably
implemented on a smart interface card, such as a smart protocol engine.
FIG. 8 is an illustration of multiple channel digital ad insertion
techniques in accordance with a second embodiment of the invention.
A plurality of video sources 800 are connected to a multi-channel
encoder/multiplexer such as an MPEG 2 or an ATM multiplexer 810. The
digital output from multiplexer 810 is fed to source switch 820 which
selects between the network feed coming through the video source 800 or
the local advertising feed originating at local digital video storage 850
via Buffer Pool and MPEG Formatter 860. The selected output for a
particular channel is fed to output port 870 for distribution by either an
ATM switch or an MPEG capable decoder, depending upon the type of
encoding.
The multiplexer may implement any number of multiplexing techniques. For
example, each video source could be applied to a separate channel of a DS3
digital multiplex group. If that were the case, then source switch 820
would be a simple channel drop and insert facility for dropping out one
channel of the DS3 composite and replacing it with information from local
digital video storage 850.
Alternatively, multiplexer 810 could be one which multiplexes ATM packets
into an OC-N fiber optic format for transmission to a destination. In such
case, source switch 820 would be a simple, selectable packet filter which
would substitute packets from local digital video storage 850 for those
originating from multiplexer 810. Multi-channel cue detector 830 scans
video sources 800 repeatedly to detect the presence of cue tones on each
source.
Multi-channel idle detector 840 monitors, in the two examples previously
given, either each time slot of a TDM composite stream to detect the
presence of idle information in each channel or monitors ATM packets for
the presence of idle information to be sent to a particular destination.
How the ad insertion is accomplished is discussed more in detail with
reference to FIG. 9.
Multi-channel detector 940, multi-channel cue detector 930, source switch
920, local digital video storage 850, buffer pool, and MPEG 2 formatter
960 all correspond to items in FIG. 8 which have the same last two digits.
Multiple channel video source information for multiplexer 810 arrives at
input port 910 and is passed to header or time slot monitor 942 of the
multi-channel detector 940. If a time slot oriented time division
multiplexer is utilized, information will be extracted from a respective
time slot at 942 and passed to idle detector 943 where the contents of the
information extracted from the time slot is examined to determine the
presence of idle data. If a series of idle time slots are detected having
idle data, bi-stable 941 is set to a state such that 1 occurs on the
output lead going to AND gate 945.
If an MPEG or ATM type multiplexer is utilized in which address information
is used to separate channels, the packet headers will be decoded to
determine the source or destination for the packets arriving from
multiplexer 810. When a number of idle packets are detected from a
particular source or for a particular destination, a bi-stable 941 is set
to the ONE condition so that a logic 1 is applied to one input of AND gate
945. By monitoring time slots individually or by monitoring packet
addresses by source address, one can detect when a particular channel goes
idle.
Multichannel cue detector 930 can be implemented in several ways. As
illustrated in FIG. 8, it can sample incoming lines repeatedly and detect
from which line a pre-roll cue is received. When a pre-rolled cue is
received for a particular line(i), a bi-stable 931(i) associated with that
line can be set to 1 thus putting a logic 1 state on one input of AND gate
945 indicating that a pre-roll cue has been received for that particular
channel. Later, when idle is detected, AND gate 945 has been pre-primed
from the pre-roll cue and when idle is detected, bi-stable 941(i) is set
to 1 and AND gate 945 is enabled thus triggering a switch of source from
input multiplexer 810 to the local source 960 which carries the local
advertising. Upon switchover, the output from the local source, is
substituted for the channel information from multiplexer 810.
If multiplexer 810 is a time division multiplexer, then individual channels
will be selected in synchronism with the incoming time division multiplex
stream. Bi-stables 941(i) and 931(i) are provided for individual timeslots
i. Source switch 920 would be switched synchronously depending on whether
or not an alternate source of data were required to be inserted in a
particular time slot.
In an environment in which MPEG is utilized for multiplexing, when
alternate sources are required, there will be no direct packet-by-packet
substitution. Rather, MPEG packets from multiplexer 810 from the source to
be substituted will be blocked and the output of local digital video
storage, in proper MPEG format will be worked into the digital stream
where ever vacancies exist.
Bi-stables 931 and 941 can be implemented either as flags, as individual
bits of a register, as individual bits of storage, or as individual flip
flops for each channel being controlled.
In operation, when the pre-roll cue is received from a particular source
800, it is detected for that particular source and multi-channel cue
detector 930 and the pre-roll bi-stable 931 is set thus priming AND gate
945 for a switch from network programming to local advertising. When
multi-channel detector 940 detects that the source for multiplexer 810 has
gone idle because the time for switching to local advertising has
occurred, bi-stable 941 is set and AND gate 945 has both inputs in logic 1
condition thus activating the source switch 920 to divert to local digital
video storage 950-960 which is an output on line 970 to the users.
By using the invention disclosed herein, the problems of the prior art are
overcome. In this disclosure, there is shown and described only the
preferred embodiment of the invention, but as aforementioned, it needs to
be understood that the invention is capable of use in various other
combinations and environments and is capable of change or modifications
within the scope of the inventive concepts as expressed herein.
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